Generally, incremental or absolute encoding schemes can be used to measure the angular position of a rotating device, such as a volume-control knob or the crown of an electronic watch. In many applications, such control elements are also axially displaceable in order to trigger or to activate various functions of a device. Therefore, it is also necessary to measure the axial position of the same knob or crown. In watch applications, the axial position of the crown is used to change the modes of the watch, such as show-time, adjust-date, and adjust-time, for example. If the crown is pulled out one discrete axial position to enter the adjust-date mode, angular rotation of the crown is then used to move from one day to the next. If the crown is pulled out two discrete axial steps, angular rotation of the crown will then be used to set the time.
With many prior art solutions for determining or measuring axial and angular positions, at least two separate sensor arrangements are required to measure the angular position on one hand and to measure the axial position on the other hand. Each of these measurement arrangements has its own design requirements in terms of volume and electrical connectivity.
In watch applications, volume is very limited. Therefore, a rather compact angular and axial sensor arrangement is highly desirable. In prior art solutions, at least two adjacent sensors relative to encoded rings placed on a rod ended by a crown are used in order to measure the angular position of said rod. Furthermore one or several sensors at the rod end inside the watch case are necessary to measure the axial position of said rod. So this sensor arrangement of the prior art occupies a large space inside the watch case, which is a drawback.